Cambridge Pod Patrol warns of harmful black swallowwort plants

In late spring, black swallowwort has shiny dark green leaves in pairs, purple star-shaped flowers and grappling, spaghetti-like roots. In July and August, the plant is covered with large green seed pods. This invasive vine threatens monarch butterflies which mistake it for milkweed, but it offers no nutrition for the larvae and caterpillars. Black swallowwort’s aggressive growth pattern displaces native plant communities, threatening many songbirds, pollinators, insects and other urban wildlife. Often found growing on chain-link fences, the vine also invades woodlands, gardens, shrubs and trees.

The most reliable way to prevent black swallowwort from taking over gardens and yards is to dig up the plant with its entire root system, put it in a tightly closed bag and dispose of it in the trash. Residents should not put it into yard waste bags or in composts. The roots will re-sprout, and the seeds are not destroyed in composting operations.

In the later stage, the green seed pods resemble chili peppers. The pods can be easily pulled off the vine before they turn brown and open up, releasing hundreds of seeds carried in the air by white fibrous fluff. The pods should be treated the same way as the roots: bagged and trashed, not composted.

For information, email fpr@cambridgema.gov or go to http://cambridgema.gov/podpatrol or http://facebook.com/cambridgepodpatrol.